The present invention relates to a laminated film bag for packaging food, which is made of a laminated film, and in particular a laminated film bag which is suitable for use as a retort pouch food.
Several kinds of conventional bags have been proposed and used for packaging food. For example, several kinds of synthetic resin films have been used therefor. However, the use of only one kind of film for the bag encounters difficulty in providing sufficient effects in order to satisfy various demands for protecting food, such as prevention of oxygen permeation, prevention of moisture evaporation, prevention of permeation by aromatic components and the like. Accordingly, laminated films have been also used to overcome these difficulties.
In particular, the shock resistance strength and the ease of tearing or ease of unsealing raises problems for food packaging bags.
When a bag in which food is packaged is dropped or subjected to a shock, the bag may rupture. If its shock resistance strength is low, the handling thereof becomes very difficult during the physical distribution stage or the like. Further, if its ease of tearing is not good, the part of the bag which serves as the opening can hardly be torn or opened with ease.
The shock-resistance strength and the ease of tearing properties of a bag compete against each other, and are not compatible with each other.
Even if a bag is formed simply with the use of laminated films in which films each having a high ease of tearing, such as uniaxially oriented films or the like are laminated together, the unsealing of the bag is unsatisfactory, causing a high manufacturing cost. When the bag formed of two such laminated films is torn, a shift is encountered during tearing since the tear directions of the two laminated films forming the bag are not precisely coincident with each other in the vertical direction. That is, one of the laminated films is torn further downward so that a vertical shift occurs. The levels of the tear at the opening of the bag do not align with each other at the front and rear sides thereof, and accordingly, there is a high tendency for the contents thereof to spill therefrom.
If a shift in the tear occurs between the front and rear sides of the bag as mentioned above, the position of the downward tear provides an opening to the bag, and accordingly, the contents of the bag spill out, raising the risk of contamination.
In particular, in the case of the packaging of a retort pouch food, the food which is heated up to a high temperature would spill so as to create the disadvantage of a high risk of heat injury.
In a process in which a laminated film is scored by a knife or a slitter, the ease of unsealing can be attained by a some degree, but the shock resistance deteriorates greatly.